Thermal switch



July 12, 1932. B, RUNYON 1,867,380.

THERMAL SWITCH Filed Jan. 4, 1929 F/G. /4 l2 9 42 FIG. 2

A TTO/PNEY Patented July 12, 1932 UNITED STATES PATENT OFFICE BENJAMINF. RUNYON, F BAYSIDE, NEW YORK, ASSIGNOR TO BELL TELEPHONE LAB-ORATORIES, INCORPORATED, 015 NEW YORK, N. Y., A CORPORATION OF NEW YORKTHERMAL SWITCH Application filed January 4, 1929. Serial No. 380,221.

This invention relates to switching apparatus and its object is toprovide a thermal-' 1y operated device in which contacts forming partsof the thermally operated switching device operating circuit areoperated for controlling theoperation of a switching device in a testingcircuit or the like in a predetermined lapse of time.

According to this invention two thermostatic bars oppose each other whensubmitted simultaneously to similar degrees of temperature variations,but operate for closing contacts with a snap under the influence of amagnet upon a certain degree of tempera- 16 ture difference in the bars.More specifically the bars are secured together at one end, and anarmature is mounted on their free ends which extends in attractablerelation to the pole-pieces of a magnet which may be either 20 of apermanent or electro-magnetic type.

Heating elements in the form of coils are adapted to heat the barsalternately to cause the operation of the movable contacts against thepull of the magnets which normally hold 25 the contacts firmly closed.

In the drawing Fig. 1 is a plan view of the relay with its protectivecasing removed.

Fig. 2 is a side view thereof showing the protective casing in section.Fig. 3 is a diagram- 80 matic view of the operating circuit of thisrelay and Fig. 4 is an enlarged view of the bimetallic bars.

In the drawing 10 indicates an elongated supporting copper plate havingan upright extension 11 adapted to support a bank of terminals as shownin Figs. 1 and 2 provided for a purpose that will be hereinafterdescribed in detail.

On plate 10 are mounted magnets 12 and 12' on the cores of which ismounted an upright support 13 of magnetic material, this support and themagnets being held on the plate 10 by screws 9 and 9 as shown in Fig.

'1. On the free ends of the cores of magnets I? 12 and 12' brackets 14and 15 are secured by screws 16, the opposite ends of these bracketsbeing secured to support 13 by screws 17 and 18 respectively. Thesebrackets are magnetically insulated from support 13 by a brassblock 15'and are held in spaced rela-' tion "on the'front end of'the magnets by abrass spacer member 19 shown in Fig. 1.

on the upright support 13 there is mounted a pair of bimetallic bars 20and 21 each having one of its ends secured tightly to the support 13from which they extend laterally in a V shaped formation. As'shown inFigs. 1, 3 and 4-on the free ends of these bars is mounted anaarmature22 which is securely held thereon by rivets 23.

On the upright portions of brackets 14 and i 15 there isadjustably-mounted a pair of pole-pieces 24 and 25 each of which isprovided with a counter nut 26 and 27 for holding the pole-pieces inadjusted position with res ect to armature 22.

n the front end of copper plate 10 there is insulatedly mounted a pairof upright I supports 28 and 29 each provided with an adjustable contactmember 30 and 31 disi posed in engageable relation with contacts 51carried by the armature 22. Contacts 30 and 31 are connected by wires 32and 33 to wire terminals 34' and 35 of the terminal bank abovementioned, the return side of the circuit for contacts 30 and 31 beingthrough the bimetallic bars 20 and 21, the lower portion of uprightsupport 13, screws 9 extending through the plate 10, upright extension11 and the terminal 36 disposed in contacting Y relation with theupright extension 11.

Bimetallic bar 21 carries a heating element 56 which is connected to thewire terminals 37 and 38,.the latter also forming a return path for theheating element 39 carried by the bimetallic bar 20, the otherconnection for this heatingelement being through wire 40 attached toterminal 41.

The electric circuit for the magnets 12 and 12 extends from terminal 42,wire 43,

magnet 12, wire 44, magnet 12, and wire attached to terminal 46.

In Fig. 3 is shown diagrammatically a suitable circuit arrangement inwhich this thermostatic relay may be used for controlling the operationof a switching device SD adapted for impressing, in predetermined lapsesof time, a high potential current on conductors enclosed or protected bya lead sheath'61. I

25 and the lower end of bracket secured at the armature end of themagnet cores. A

"circuit is also closed through the heating element 56 from one side ofthe battery through the switch wiper 4:7, terminal 38, the heatingelement, terminal 37, the closed wiper of switching device 48 and backto the other side of battery 49. Another circuit is closed through oneside of battery 49, wiper 47, terelement 39.

minal 36, plate 10, support 13, the bimetallic bars 20 and 21, thearmature 22, contacts 51 and 31, wire 83, attached to terminal 35, thewiper of switching device SD, the conductor "70 enclosed in lead sheath61, the signaling device 62, and the other side of battery 49. Underthis circuit condition and supposing the insulation of the conductor 70is defective, the current will flow through signalling device 62 forindicating a break in the insulation of the conductor. However, if theinsulation of the conductor is in good condition the signalling device62 is not operated. Upon the switching of the current in heating element56 by the closure of switch 47 the bimetallic bar 21 becomes therebyheated to a point so as to move the armature and the contact carriedthereby in'engageable relation with, contact 30 against the magneticattraction of pole-piece which causes the armature to move with asnapping action due to the tension acquired to overcome the pull ofmagnets.

The closure of contact 51 with contact energizes magnet through anobvious circuit, the energization of this magnet being effective tooperate the switching device 48 to open the clrcuit of heating element56 to permit the cooling of bimetallic bar 21 and simultaneously closingthe circuit of heating The bimetallic bar 20 is thus heated to a pointsuflicient to overcome the pull or attraction of the magnet for movingthe armature 22 and the contact carried thereby in reengagement withcontact 31 and thus causing the eenergization of magnet 50 to permit theswitching device 48 to return to normal under the action of itsretracting spring 60. The back and forth movement of the magneticarmature under control of the bimetallic bars being effective to movethe wiper of switch SD one step onto an auxiliary terminal of theswitching device SD.

It is to be noted that by the use of a heating element on eachbimetallic bar such a device is not entirely dependent for operationupon the-alternating dissipation of the latent heat in the bars. Thesebars are caused to operate under the combined effects of the heaterelements thus making it possible to obtain the operation of the contactscarried by the armature 22 in very accurate periods of time. Theconnection of the heating elements in parallel with the magnetseffectively compensate for voltage variations in the current supplysource, because a change in the action of the magnets due to voltagefluctuations correspondingly affects the opera tion of the bimetallicbars, and the voltage fluctuations therefore have no elfect on theoperating time of the device.

In this device the provision of two bimetallic bars oflers means forcompensating for differences in temperature of the atmosphere since theheat efiect in one bar is compensated by a similar heat eifect in theother bar and therefore the armature is not deviated from its normaladjusted position by similar changes in the bar temperatures, while theparticular method used for holding these bars on their supportingmember, avoids rigidity in the structure of the thermostatic elementwhich is thus permitted to move in a positive manner in response to afew degrees temperature diiference in the bars.

What is claimed is z w 1. In combination a magnet having op posedpole-pieces, a support, a pair of bimetallic bars secured together onsaid support and extending in a V formation therefrom to form a pivotalpoint for the bars, a heating coil on each bar, an armature for saidmagnet secured to said bars and extending between said pole pieces,circuits, each including one of said heating coils, a two-positionswitch controlled by the bimetallic bars and in each position closing acircuit through one heating coil, whereby circuits are successivelyclosed through said heating coils to cause the bimetallic bars to flexat their point of support for actuating the armature.

2. In a thermal switch, a supporting plate, a pair of bimetallic barssecured together at one end of said plate and the free ends extending ina flared formation therefrom, a magnet having opposed pole-pieces,'anarmature for said magnet mounted on said bars and having a contact, apair of contacts mounted on said plates and adapted to be engaged bysaid armature contact, heating coils on said bars, circuits, eachincluding one of said coils, a two-point switch controlled by said barsand in each position closing a circuit through one of said coils forcausing the operation of said bars, the magnet causing the bars toengage the contacts with a snapping action.

3. A thermal switch characterized. in this that bimetallic bars havingheating coils are disposed in a V formation and attached to a support toform a pivotal point for the bars, these bars carrying a contact foralternately engaging contacts carried by the support.

In witness whereof, I hereunto subscribe my name this 2nd day ofJanuary, 1929.

BENJAMIN F. RUN YON.

